According to Arthur Gent, 'F-B The Complete Story' (copies available), the frame prefix for 1962 was C (not Ch) for the Plover 86. You will need an AMC 15T engine expert to confirm that the engine serial number is correct for this year.

Frame with a C is as said above 1962 year model August 1961 to July 1962engine No also dates to late 1961 so possibly an original pairing ? but no factory records to back this up exist !Again as said above the "H" is a mystery and should not be there ?JH